Method for producing flavorful and aromatic compounds from tobacco

ABSTRACT

The invention provides a method of producing flavorful and aromatic compounds from tobacco by (1) adjusting the pH of an aqueous composition comprising water and a tobacco material to at least about 6 using a nitrogen-free base, such as an alkali metal hydroxide; and (2) heating the pH-adjusted aqueous composition for a time and under conditions sufficient to produce flavorful and aromatic compounds, such as pyrazines. A reducing sugar can be added to the aqueous tobacco composition to further increase the amount of flavorful and aromatic compounds produced. The tobacco material in the aqueous tobacco composition may comprise solid tobacco particles or an aqueous tobacco extract in either liquid form or in the form of spray-dried particles. The treated aqueous composition can be applied to a smokable material during the manufacture of a smoking article, such as a cigarette.

FIELD OF THE INVENTION

[0001] The invention relates to tobacco, and in particular, to methods for processing tobacco materials in a manner that produces flavorful and aromatic compounds.

BACKGROUND OF THE INVENTION

[0002] Popular smoking articles, such as cigarettes, have a substantially cylindrical rod shaped structure and include a charge, roll or column of smokable material such as shredded tobacco (e.g., in cut filler form) surrounded by a paper wrapper thereby forming a so-called “tobacco rod.” Normally, a cigarette has a cylindrical filter element aligned in an end-to-end relationship with the tobacco rod. Typically, a filter element comprises plasticized cellulose acetate tow circumscribed by a paper material known as “plug wrap.” Certain cigarettes incorporate a filter element having multiple segments, and one of those segments can comprise activated charcoal particles. Typically, the filter element is attached to one end of the tobacco rod using a circumscribing wrapping material known as “tipping paper.” It also has become desirable to perforate the tipping material and plug wrap, in order to provide dilution of drawn mainstream smoke with ambient air. A cigarette is employed by a smoker by lighting one end thereof and burning the tobacco rod. The smoker then receives mainstream smoke into his/her mouth by drawing on the opposite end (e.g., the filter end) of the cigarette.

[0003] The tobacco used for cigarette manufacture is typically used in blended form. For example, certain popular tobacco blends, commonly referred to as “American blends,” comprise mixtures of flue-cured tobacco, burley tobacco and Oriental tobacco, and in many cases, certain processed tobaccos, such as reconstituted tobacco and processed tobacco stems. The precise amount of each type of tobacco within a tobacco blend used for the manufacture of a particular cigarette brand varies from brand to brand. However, for many tobacco blends, flue-cured tobacco makes up a relatively large proportion of the blend, while Oriental tobacco makes up a relatively small proportion of the blend. See, for example, Tobacco Encyclopedia, Voges (Ed.) p. 44-45 (1984), Browne, The Design of Cigarettes, 3^(rd) Ed., p.43 (1990) and Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) p. 346 (1999).

[0004] In order to improve the flavor and aroma of tobacco materials used in smoking article manufacture, it is desirable to add flavorful and aromatic compounds, such as pyrazines, aminosugars, and Amadori compounds, to the tobacco material. Various methods for producing such compounds are known in the art. For example, U.S. Pat. No. 6,499,489, which is incorporated by reference herein in its entirety, describes a method for generating a flavorful tobacco composition by treating a tobacco suspension with ammonia and heating the treated suspension. The heat treatment produces an environment conducive for Maillard Reactions or “browning reactions”. The Maillard Reactions are reactions between (i) the amino substituent of amino acids, peptides, proteins or other nitrogen-containing compounds, and (ii) the carbonyl group of a sugar in the reducing form or other carboxyl-containing compounds present in the tobacco composition. Such reactions result in a significant darkening of the tobacco composition, typically to an extremely dark brown color. See e.g., Maillard, Ana. Chim., Vol. 9, pp. 5 and 258 (1916); Hodge, J. Agric. Food Chem., Vol. 1, p. 928 (1953); Nursten, Food Chem., Vol. 6, p. 263 (1981) and Waller et al, ACS Symp. Ser. (1983).

[0005] It would be desirable in the art to provide further methods for improving the flavor and aroma of tobacco compositions.

SUMMARY OF THE INVENTION

[0006] The present invention provides a method of producing flavorful and aromatic compounds from tobacco by heating an aqueous tobacco composition at an alkaline pH. The aqueous tobacco composition is heated for a time and under conditions sufficient to produce flavorful and aromatic compounds, such as pyrazines. Surprisingly, it has been discovered that significant amounts of pyrazine compounds can be produced using a nitrogen-free base to increase the pH of the aqueous tobacco composition to alkaline levels. Prior to the present invention, ammonia sources, which provide a source of nitrogen that can participate in reactions that produce aminosugars and pyrazines, were used as the pH-adjusting material. In the present invention, exogenous nitrogen sources such as ammonia are eliminated from the process without sacrificing production of desirable compounds.

[0007] The tobacco material used in the aqueous tobacco composition may comprise solid tobacco, such as whole tobacco in particulate form, or one or more aqueous tobacco extracts. If an aqueous tobacco extract is used, the extract can be used in liquid form or in the form of spray-dried particles. Typically, the tobacco material is present at a concentration of about 5 to about 90% by weight, more preferably about 10 to about 80% by weight.

[0008] The amount of nitrogen-free base added to the aqueous tobacco composition is sufficient to raise the pH of the aqueous composition to at least about 6, preferably at least about 9, more preferably at least about 10, and most preferably at least about 11. The pH-adjusted aqueous composition is preferably heated at a temperature of about 80° C. to about 150° C., more preferably about 95° C. to about 130° C. The aqueous composition is generally heated for about 30 minutes to about 3 hours, more preferably about 30 minutes to about 1.5 hours.

[0009] Following heat treatment, the treated aqueous composition may be applied to a smokable material during the manufacture of smoking articles, such as cigarettes. For example, the heated aqueous composition may be added to tobacco lamina or cut filler as a top dressing or casing. Alternatively, where the heated aqueous composition comprises a tobacco extract, the treated aqueous composition may be recombined with a solid tobacco sheet to form a reconstituted tobacco material.

[0010] In a preferred embodiment, in order to boost the production of flavorful and aromatic compounds, a reducing sugar is added to the aqueous composition. Exemplary reducing sugars include glucose, fructose, sucrose, mannose, galactose, rhamnose, and mixtures thereof. The reducing sugar may be in a pure form or an unrefined form (e.g., high fructose corn syrup).

DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention now will be described more fully hereinafter. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0012] The invention is directed to a method for producing flavorful and aromatic compounds from tobacco by treating an aqueous tobacco composition comprising water and a tobacco material with a nitrogen-free base and heating the resulting composition. As used herein, the term “tobacco material” includes solid pieces of whole tobacco (i.e., tobacco including both the water-soluble portion and the insoluble pulp as in tobacco cut filler or lamina) as well as aqueous extracts of tobacco. The tobacco material may be derived from any type of tobacco, such as flue-cured tobacco, burley tobacco, Oriental tobacco, Maryland tobacco, dark tobacco, dark-fired tobacco and Rustica tobaccos, as well as other rare or specialty tobaccos, or blends thereof. See, for example, Akehurst, Tobacco (1968) and Tso, Production, Physiology, and Biochemistry of Tobacco Plant (1990).

[0013] The type of flue-cured tobacco can vary. Descriptions of flue-cured tobaccos, growing practices, harvesting practices and curing practices are set forth in Hawks, Principles of Flue-Cured Tobacco Production (1978), Sumner et al., Guidelines for Temperature, Humidity, and Airflow Control in Tobacco Curing, Univ. Georgia Res. Bull. 299 (1983), Todd, Flue-Cured Tobacco—Producing a Healthy Crop (1981), Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) (1999), Flue-Cured Tobacco Information, NC Coop. Ext. Serv. (2002) and US Pat. App. Pub. 2001/0000386 to Peele. Flue-cured tobaccos are also referred to as Virginia, bright or blond tobaccos. Representative flue-cured tobaccos include Coker 48, Coker 176, Coker 371-Gold, Coker 319, Coker 347, GL 939, K 149, K 326, K 340, K 346, K 358, K 394, K 399, K 730, NC 27NF, NC 37NF, NC 55, NC 60, NC 71, NC 72, NC 82, NC 95, NC 297, NC 606, NC 729, NC 2326, McNair 373, McNair 944, Ox 207, Ox 414 NF, Reams 126, Reams 713, Reams 744, RG 8, RG 11, RG 13, RG 17, RG 22, RG 81, RG H4, RG H51, Speight H-20, Speight G-28, Speight G-58, Speight G-70, Speight G-108, Speight G-111, Speight G-117, Speight 168, Speight 179, Speight NF-3, Va 116 and Va 182. Preferred flue-cured tobaccos are those that are cured using the types of techniques and conditions set forth in US Pat. App. Pub. 2001/0000386 to Peele. Preferred flue-cured tobaccos are aged for at least one year after curing is complete.

[0014] The type of burley tobacco can vary. Descriptions of burley tobaccos, growing practices, harvesting practices and curing practices are set forth in Wiernik et al, Rec. Adv. Tob. Sci., Vol. 21, p. 39-80 (1995), Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) (1999) and Burley Tobacco Information, NC Coop. Ext. Serv. (2002). Representative burley tobaccos include Clay 402, Clay 403, Clay 502, Ky 14, Ky 907, Ky 910, Ky 8959, NC 2, NC 3, NC 4, NC 5, NC 2000, Tn 86, Tn 90, Tn 97, R 610, R 630, R 711, R712, NCBH 129, Bu 21×Ky 10, HB04P, Ky 14×L 8, Kt 200, Newton 98, Pedigo 561, Pf 561 and Va 509. Preferred burley tobaccos are air cured. Preferred air cured burley tobaccos are aged for at least one year after curing is complete.

[0015] The Oriental tobacco used in the invention can vary. Descriptions of Oriental-type tobaccos, growing practices, harvesting practices and curing practices are set forth in Wolf, Aromatic or Oriental Tobaccos (1962), Akehurst, Tobacco (1968), Tobacco Encyclopedia, Voges (Ed.) (1984), Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) (1999). Oriental-type tobaccos also are referred to as Greek, aromatic and Turkish tobaccos. Representative Oriental-type tobaccos include the Izmir, Basma, Mavra and Samsun varieties. Other representative Oriental-type tobaccos include Trabzon, Thesalian, Tasova, Sinop, Izmit, Hendek, Edirne, Semdinli, Adiyanman, Yayladag, Iskenderun, Duzce, Macedonian, Katerini, Prilep, Krumovgrad, Bafra, Bursa, Bucak, Bitlis and Balikesir tobaccos, as well as the so-called semi-Oriental tobaccos such as Sebinkarahisar, Borgka and East Balkan tobaccos. Although Oriental-type tobaccos that are employed in accordance with the present invention can be grown in a variety of locations throughout the world, typical Oriental tobaccos are grown in eastern Mediterranean regions such as Turkey, Greece, Bulgaria, Macedonia, Syria, Lebanon, Italy, Yugoslavia, and Romania. Preferred Oriental tobaccos are sun cured. Preferred sun cured Oriental tobaccos are aged for at least one year after curing is complete.

[0016] The type of Maryland tobacco can vary. Descriptions of Maryland tobaccos, growing practices, harvesting practices and curing practices are set forth in Tobacco Encyclopedia, Voges (Ed.) (1984), Aycock et al., Maryland Coop. Ext. (1984), Aycock et al., Maryland Coop. Ext. (1995), and Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) (1999). Representative Maryland tobaccos include Md 10, Md 40, Md 201, Md 609, Md 872 and Md 341. Preferred Maryland tobaccos are air cured, and often are referred to as light air cured tobaccos. Preferred air cured Maryland tobaccos are aged for at least one year after curing is complete.

[0017] In embodiments utilizing solid pieces of whole tobacco in the aqueous composition, the physical form of the tobacco can vary. Most preferably, the tobaccos are those that have been appropriately cured and aged. Most preferably, the tobaccos are used in forms, and in manners, that are traditional for the blending of tobaccos for use as cut filler for the manufacture of smoking articles, such as cigarettes. The tobacco can be used in whole leaf form. The tobacco also can be used in the form of laminae or strip. The tobacco also can have a shredded or cut filler form. The tobacco can have a processed form, such as processed tobacco stems (e.g., cut-rolled or cut-puffed stems), volume expanded tobacco (e.g., puffed tobacco, such as dry ice expanded tobacco (DIET), preferably in cut filler form), or reconstituted tobacco (e.g., reconstituted tobaccos manufactured using paper-making type or cast sheet type processes, preferably in strip or cut filler form). In a preferred embodiment, the tobacco is in the form of tobacco waste materials, such as fines, dust, scrap and stem. The tobacco material utilized in the present invention can also be mixtures or blends of one or more of the tobacco forms described above.

[0018] In one embodiment, the solid tobacco material is in the form of finely-divides particles such that the aqueous composition is in the form of a tobacco suspension or slurry. The aforementioned tobacco material can be subjected to various means to reduce its size, such as grinding, such that the resulting tobacco material is a finely ground tobacco dust or powder. Various grinding techniques will be apparent to one skilled in the art, and may include the use of, e.g., ball mills or hammer mills. The grinding may also be carried out under vibrating or agitating conditions, the selection of said conditions being within the skill of one in the art. As used herein, the term “finely ground tobacco material” refers to tobacco materials composed of particles that are less than 10 mesh, preferably less than 20 mesh, and most preferably are less than 40 mesh (standard sieve size). That is, the fine particles most preferably can pass a 40 mesh (Tyler) screen. Alternatively, the tobacco material may already be in dust form such that additional grinding is not necessary.

[0019] In another embodiment, the tobacco material comprises one or more aqueous tobacco extracts derived from any type of tobacco, such as aqueous extracts of flue-cured tobacco, aqueous extracts of burley tobacco, aqueous extracts of Oriental tobacco, aqueous extracts of Maryland tobacco, and mixtures thereof. In one preferred embodiment, the aqueous tobacco composition comprises a mixture of an aqueous extract of flue-cured tobacco and an aqueous extract of burley tobacco. As noted in the appended examples, use of a mixture of an aqueous burley tobacco extract and an aqueous flue-cured tobacco extract can increase the production of flavorful and aromatic compounds due to reaction of the natural sugar sources in the flue-cured extract with the natural nitrogen sources in the burley extract. Typically, when a mixture of extracts is used, each extract is present at a concentration of about 10 to about 90 percent by weight based on the total weight of the tobacco extracts in the aqueous composition, preferably about 20 to about 80 percent by weight, most preferably about 30 to about 60 percent by weight.

[0020] As known in the art, aqueous tobacco extracts are typically formed during production of reconstituted tobacco materials. Tobacco reconstitution processes traditionally convert portions of tobacco that normally might be wasted into commercially useful forms. For example, tobacco stems, pieces of tobacco scrap and tobacco dust can be used to manufacture reconstituted tobaccos of fairly uniform consistency. In a typical paper making reconstituted tobacco process, tobacco is extracted with water, and the resulting aqueous extract and water insoluble pulp are separated from one another. The pulp portion can be refined to a desired consistency, and formed into a mat or web (much like wood pulp fibers in a traditional paper making process). The separated aqueous extract can be used as the tobacco material in the aqueous composition in the method of the present invention. Following treatment according to the present invention, the aqueous tobacco extract is applied to the mat of insoluble pulp, and the overall resulting mixture is dried to provide a reconstituted tobacco sheet incorporating the tobacco components from which that sheet was derived. Typically, tobacco stems are used in making such a reconstituted tobacco sheet, because the fibrous nature of those stems provides strength and structural integrity to the resulting sheet. Processes for forming reconstituted tobacco sheets are described, for example, in U.S. Pat. Nos. 4,987,906 and 5,501,237.

[0021] The aqueous composition utilized in the method of the invention is formed by mixing a liquid having an aqueous character with the tobacco material. The liquid can consist primarily of water, normally greater than about 90 percent water by weight, and can be essentially pure water. For example, the liquid can be distilled or de-ionized water, tap water, or the like. As noted above, the tobacco material may comprise an aqueous extract of tobacco (in liquid or solid form) or solid pieces of whole tobacco (e.g., tobacco in particulate form). The water mixed with the tobacco material to form the aqueous composition may include minor amounts of various additives known in the art, such as surfactants, organic solvents or humectants. The aqueous composition preferably comprises about 5 to about 90 percent by weight tobacco material, based on the total weight of the aqueous composition, more preferably about 10 to about 80 percent by weight, most preferably about 20 to about 70 percent by weight.

[0022] If desired, in addition to the aforementioned tobacco materials and water, the aqueous composition of the present invention can further include other components. However, no additional reagents are required to produce flavorful and aromatic compounds according to the method of the invention. Optional components include casing materials (e.g., sugars, glycerine, cocoa and licorice) and top dressing materials (e.g., flavoring materials, such as menthol). The selection of particular casing and top dressing components is dependent upon factors such as the sensory characteristics that are desired, and the selection of those components will be readily apparent to those skilled in the art of cigarette design and manufacture. See, Gutcho, Tobacco Flavoring Substances and Methods, Noyes Data Corp. (1972) and Leffingwell et al., Tobacco Flavoring for Smoking Products (1972).

[0023] In a preferred embodiment of the invention, reducing sugars, such as glucose, fructose, sucrose, mannose, galactose, rhamnose, or mixtures thereof, are added to the aqueous composition. The addition of exogenous reducing sugars to the aqueous composition can increase the yield of flavorful compounds, such as pyrazines. As used herein, “exogenous” refers to sources external to the tobacco material in the aqueous composition. The reducing sugar can be in a pure form or in unrefined form, such as high fructose corn syrup (HFCS), which has a high concentration of fructose. Many derivatives of reducing sugars can also be used, such as phosphate-substituted reducing sugars (e.g., glucose-6-phosphate, fructose-6-phosphate, and fructose-1,6-diphosphate). Reducing sugars can also be provided in the form of precursors that can readily release reducing sugars under the reaction conditions employed in the method of the invention. Examples of suitable precursors include disaccharides, polysaccharides, and derivatives thereof. In such cases, reducing sugars are generated by the hydrolysis of the disaccharides or polysaccharides. Alternatively, a combination of a hydroxyketone and an aldehyde can be used as a reducing sugar precursor, as taught in U.S. Pat. No. 6,325,860. Typically, the reducing sugar is present in an amount between about 1 to about 20 percent by weight based on the total weight of the aqueous composition, more preferably about 1 to about 15 percent by weight, most preferably about 2 to about 10 percent by weight. Generally, when pure sugar sources are used, smaller amounts are needed in order to produce the same amount of flavorful and aromatic compounds as compared to unrefined sugar sources, such as HFCS.

[0024] It is preferable to avoid the addition of exogenous nitrogen sources to the aqueous composition, such as nitrogen-containing bases or amino acids. The present invention relies primarily on the reaction of naturally occurring nitrogen-containing compounds and sugar compounds present in the tobacco material. However, although less preferred, added amounts of amino acids, such as threonine, serine, leucine, isoleucine, and valine, can be used without departing from the present invention.

[0025] Typically, without the addition of any pH adjusting materials, the pH of the aqueous composition of the invention is about 4.5 to about 6 due to the acidic nature of tobacco. In the method of the present invention, the pH of the aqueous composition is increased to at least about 6 by addition of a nitrogen-free base. By increasing the alkalinity of the aqueous composition, reactions that produce flavorful and aromatic compounds are promoted. By “nitrogen-free” is meant a base that does not contain any nitrogen atoms. In particular, the term “nitrogen-free” excludes bases such as ammonia, ammonium hydroxide, urea, and the like. The term “base” is used herein to broadly refer to organic or inorganic compounds capable of increasing the pH of an aqueous solution to alkaline levels. Exemplary nitrogen-free bases include hydroxides of alkali metals or alkaline earth metals (e.g., sodium hydroxide, potassium hydroxide), carbonates of alkali metals or alkaline earth metals (e.g., sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate), and alkoxides of alkali metals or alkaline earth metals (e.g., sodium methoxide, potassium methoxide). Preferably, the base is a hydroxide, such as sodium hydroxide or potassium hydroxide.

[0026] Following adjustment with the nitrogen-free base, the final pH of the aqueous composition is preferably about 6 to about 14, more preferably about 8 to about 14, most preferably about 9 to about 12. In preferred embodiments, the pH is at least about 9, more preferably at least about 10, and most preferably at least about 11.

[0027] The pH-adjusted aqueous composition is exposed to heat. The aqueous composition can be heated using any heating method or apparatus known in the art. In a preferred embodiment, the aqueous composition is heated in a microwave oven. The aqueous tobacco composition should be heated at a temperature sufficiently high to produce flavorful and aromatic compounds, such as pyridines, pyrazines, Amadori compounds, aminosugars, and, to a lesser extent, sugar thermal degradation products such as substituted furans and diketones. In particular, the heat treatment should produce an environment conducive for Maillard Reactions or “browning reactions”. The temperature of the heat treatment is generally about 25° C. to about 200° C. A preferred range is about 80° C. to about 150° C., more preferably about 95° C. to about 130° C.

[0028] The amount of time that the aqueous tobacco composition is subjected to the temperature treatment can vary. The time period should be sufficient to produce flavorful and aromatic compounds. Generally, the amount of time required to produce a significant amount of the desired flavorful and aromatic compounds varies inversely with the treatment temperature, meaning shorter treatment periods can be coupled with higher treatment temperatures and vice versa. Typically, the heat treatment period is about 30 minutes to about 3 hours, although longer or shorter treatment periods could also be used without departing from the invention. In a preferred embodiment, the heat treatment time period is about 30 minutes to about 1.5 hours.

[0029] The heat treatment preferably occurs at atmospheric pressure using, for example, a vented tank. It is most convenient and preferable for the process steps to be carried out without taking special care to control the pressure of the atmosphere that surrounds the tobacco material (i.e., the process steps can be carried out under normal atmospheric pressure conditions), and without taking special steps to control the make up of the atmosphere that surrounds the tobacco (i.e., the process steps can be carried out in normal atmospheric air). However, a pressure-controlled environment can be used without departing from the invention. Such an environment is provided, for example, by enclosing the aqueous tobacco composition in an air-sealed vessel or chamber. Typically, a pressure-controlled environment is provided using a pressure vessel or chamber capable of withstanding relatively high pressures. Preferred pressure vessels are equipped with an external heating source. Examples of vessels that provide a pressure-controlled environment include a high pressure autoclave from Berghof/America Inc. of Concord, Calif., and Parr Reactor Model Nos. 4522 and 4552 available from The Parr Instrument Co. and described in U.S. Pat. No. 4,882,128 to Hukvari et al. Operation of such exemplary vessels will be apparent to the skilled artisan. See, for example, U.S. Pat. No. 6,048,404 to White. Typical pressures experienced by the aqueous tobacco composition during such a pressure-controlled heating process conducted in such vessels often range from about 10 psig to about 1,000 psig, normally from about 20 psig to about 500 psig.

[0030] Atmospheric air, or ambient atmosphere, is the preferred atmosphere for carrying out the present invention. However, heating treatment of the aqueous composition can also take place under a controlled atmosphere, such as a generally inert atmosphere. Gases such as nitrogen, argon and carbon dioxide can be used. Alternatively, a hydrocarbon gas (e.g., methane, ethane or butane) or a fluorocarbon gas also can provide at least a portion of a controlled atmosphere in certain embodiments, depending on the choice of treatment conditions and tobacco materials.

[0031] The composition resulting from the method of the invention contains flavorful and aromatic compounds useful as additives in the manufacture of smoking articles. Thus, tobacco materials processed according to the present invention can be used for the manufacture of tobacco products, and most preferably, smoking articles, such as cigarettes. For example, the treated aqueous tobacco composition can be added to a smokable material, such as tobacco lamina or cut filler, in the form of a casing ingredient or top dressing. The amount of the treated aqueous tobacco composition employed per smoking article can vary. Typically, for cigarettes having about 0.6 g to about 1 g of smokable material per rod, about 0.1 to about 10 percent by weight, preferably about 0.5 to about 5 percent, of the treated aqueous tobacco composition is added, based on the total weight of the smokable material in the cigarette. Representative tobacco blends, representative cigarette components, and representative cigarettes manufactured therefrom, are set forth in U.S. Pat. Nos. 4,836,224 to Lawson et al.; 4,924,888 to Perfetti et al.; 5,056,537 to Brown et al.; 5,220,930 to Gentry; and 5,360,023 to Blakley et al.; US Pat. application 2002/0000235 to Shafer et al.; and PCT WO 02/37990. Those tobacco materials also can be employed for the manufacture of those types of cigarettes that are described in U.S. Pat. Nos. 4,793,365 to Sensabaugh; 4,917,128 to Clearman et al.; 4,947,974 to Brooks et al.; 4,961,438 to Korte; 4,920,990 to Lawrence et al.; 5,033,483 to Clearman et al.; 5,074,321 to Gentry et al.; 5,105,835 to Drewett et al.; 5,178,167 to Riggs et al.; 5,183,062 to Clearman et al.; 5,211,684 to Shannon et al.; 5,247,949 to Deevi et al.; 5,551,451 to Riggs et al.; 5,285,798 to Banerjee et al.; 5,593,792 to Farrier et al.; 5,595,577 to Bensalem et al.; 5,816,263 to Counts et al.; 5,819,751 to Barnes et al.; 6,095,153 to Beven et al.; 6,311,694 to Nichols et al.; and 6,367,481 to Nichols, et al.; and PCT WO 97/48294 and PCT WO 98/16125. See, also, those types of commercially marketed cigarettes described Chemical and Biological Studies on New Cigarette Prototypes that Heat Instead of Burn Tobacco, R. J. Reynolds Tobacco Company Monograph (1988) and Inhalation Toxicology, 12:5, p. 1-58 (2000).

[0032] Alternatively, where the tobacco material in the treated aqueous tobacco composition is in particulate form (i.e., a tobacco slurry or suspension), a reconstituted cast sheet of tobacco can be formed using the treated composition. For example, a cast sheet can be formed by pouring the treated tobacco slurry onto a surface, such as a metal sheet. The slurry then is heated to evaporate the water and a dry reconstituted tobacco sheet results. Adhesive materials can be incorporated into the slurry in order to provide a tobacco sheet having good strength and structural integrity.

Experimental

[0033] The present invention is more fully illustrated by the following examples, which are set forth to illustrate the present invention and are not to be construed as limiting thereof. In the following examples, μg means micrograms, mg means milligrams, g means grams, L means liters, mL means milliliters, and HFCS means high fructose corn syrup.

[0034] In each example, heat treatment was conducted in a microwave oven manufactured by CEM Corporation, Model Mars X, under the same general conditions described in U.S. Pat. No. 6,499,489 B1. After heat treatment, headspace analysis was conducted in a method similar to that reported in Coleman et al., J. Chrom. Sci. 32:323 (1994), which is incorporated by reference herein in its entirety. For each sample, 1.0 mL was placed in a 5 mL sparge tube along with 1 mL of an aqueous standard containing 21.8 mg/L cyclohexanone as an internal standard. The yield of volatiles was calculated based on the total ion current (TIC) response of cyclohexanone. The headspace sampling parameters were the same as disclosed in U.S. Pat. No. 6,499,489 B1.

EXAMPLE 1

[0035] Analysis of pyrazine yield in the headspace above heated samples of a mixture of a liquid aqueous extract of burley tobacco (30 g) and water (5 g) was conducted at several pH levels (4.6, 6, 8, and 10). The pH of the sample was adjusted to by drop-wise addition of 50% aqueous NaOH with continuous stirring. The samples were heated for 60 minutes at a temperature of 100° C. A dramatic increase (>10×) in pyrazine yield (μg/g) in the headspace was observed at basic pH (between pH of 8 and 10).

EXAMPLE 2

[0036] The same as Example 1, except 2.5 g or 5 g of HFCS was added to each sample prior to heating. The amount of water added to the aqueous composition was reduced by the amount of HFCS (i.e., the total amount of added water and HFCS equaled 5 g). Again, a dramatic increase (>10×) in pyrazine yield (μg/g) in the headspace was observed at basic pH (between pH of 8 and 10). The addition of the HFCS increased the overall yield of pyrazines as compared to Example 1.

EXAMPLE 3

[0037] The same as Example 1, except 1 g or 2 g of rhamnose, instead of HFCS, was added to each sample prior to heating. Again, a dramatic increase (>10×) in pyrazine yield (μg/g) in the headspace was observed at basic pH (between pH of 8 and 10). The addition of rhamnose increased the overall yield of pyrazines as compared to Example 1.

EXAMPLE 4

[0038] The same as Example 1, except the pH of each sample was adjusted with 50% aqueous KOH. Again, a dramatic increase (>10×) in pyrazine yield (μg/g) in the headspace was observed at basic pH (between pH of 8 and 10).

EXAMPLE 5

[0039] The same as Example 4, except the 5 g of water was replaced with 5 g of HFCS in each sample. Again, a dramatic increase (>10×) in pyrazine yield (μg/g) in the headspace was observed at basic pH (between pH of 8 and 10). The addition of the HFCS increased the overall yield of pyrazines as compared to Example 4. The pyrazine yield produced in this experiment was higher than the pyrazine yield in comparable Example 2, suggesting that the selection of the base cation influences pyrazine yield.

EXAMPLE 6

[0040] The same as Example 4, except 2 g of rhamnose was added to each sample. Again, a dramatic increase (>10×) in pyrazine yield (μg/g) in the headspace was observed at basic pH (between pH of 8 and 10). The addition of the rhamnose increased the overall yield of pyrazines as compared to Example 4. The pyrazine yield produced in this experiment was higher than the pyrazine yield in comparable Example 3, suggesting that the selection of the base cation influences pyrazine yield.

EXAMPLE 7

[0041] Analysis of pyrazine yield in the headspace above heated samples of a mixture of a liquid aqueous extract of burley tobacco and a liquid aqueous extract of flue-cured tobacco (30 g total extract in each sample) was conducted at several pH levels (˜4.6, 6, 8, and 10). Samples containing equal amounts of each extract and samples containing a predominant amount (22.5 g) of one of the extracts were tested. The pH of the sample was adjusted to by drop-wise addition of either 50% aqueous NaOH with continuous stirring. The samples were heated for 60 minutes at a temperature of 100° C. or 125° C.

[0042] A dramatic increase (>10×) in pyrazine yield (μg/g) in the headspace was observed at basic pH (between pH of 8 and 10). Combination of both a flue-cured aqueous extract with a burley aqueous extract increased the pyrazine yield as compared to treatment of a burley aqueous extract alone, suggesting that the natural sugar sources in the flue-cured extract reacted with the natural nitrogen sources in the burley extract to produce pyrazines. Increasing the treatment temperature to 125° C. increased the pyrazine yield.

EXAMPLE 8

[0043] Analysis of pyrazine yield in the headspace above heated samples of a mixture of spray-dried particles of an aqueous burley tobacco extract (3 g) and de-ionized water (30 mL) was conducted at several pH levels (5.6, 8, and 10). The pH of the sample was adjusted to by drop-wise addition of 50% aqueous NaOH with continuous stirring. The samples were heated for 60 minutes at a temperature of 100° C. or 125° C. A small increase in pyrazine yield (μg/g) in the headspace was observed at basic pH (between pH of 8 and 10).

EXAMPLE 9

[0044] The same as Example 8, except 2.5 g or 5 g of HFCS was added to each sample. A dramatic increase (>10×) in pyrazine yield (μg/g) in the headspace was observed at basic pH (between pH of 8 and 10). The addition of the HFCS increased the overall yield of pyrazines as compared to Example 8.

EXAMPLE 10

[0045] The same as Example 8, except 1 g or 2 g of rhamnose was added to each sample. A dramatic increase (>10×) in pyrazine yield (μg/g) in the headspace was observed at basic pH (between pH of 8 and 10). The addition of the rhamnose increased the overall yield of pyrazines as compared to Example 8.

[0046] Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing description. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. 

What is claimed:
 1. A method of producing flavorful and aromatic compounds from tobacco, comprising: providing an aqueous tobacco composition comprising water and a tobacco material; adding an amount of a nitrogen-free base to the aqueous composition sufficient to increase the pH of the aqueous composition to at least about 6; and heating the aqueous composition for a time and under conditions sufficient to produce flavorful and aromatic compounds.
 2. The method of claim 1, wherein the tobacco material comprises solid pieces of whole tobacco.
 3. The method of claim 2, wherein the tobacco is in particulate form.
 4. The method of claim 1, wherein the tobacco material comprises at least one aqueous tobacco extract.
 5. The method of claim 4, wherein the at least one aqueous tobacco extract is selected from the group consisting of aqueous extracts of flue-cured tobacco, aqueous extracts of burley tobacco, aqueous extracts of Oriental tobacco, aqueous extracts of Maryland tobacco, and mixtures thereof.
 6. The method of claim 1, wherein the tobacco material is present at a concentration of about 5 to about 90 percent by weight based on the weight of the aqueous tobacco composition.
 7. The method of claim 1, wherein the tobacco material is present at a concentration of about 10 to about 80 percent by weight based on the weight of the aqueous tobacco composition.
 8. The method of claim 1, wherein the nitrogen-free base is selected from the group consisting of hydroxides of an alkali metal or an alkaline-earth metal, carbonates of an alkali metal or alkaline earth metal, and alkoxides of an alkali metal or alkaline earth metal.
 9. The method of claim 1, wherein the nitrogen-free base is sodium hydroxide or potassium hydroxide.
 10. The method of claim 1, wherein said adding step comprises adding sufficient nitrogen-free base to increase the pH to at least about
 9. 11. The method of claim 1, wherein said adding step comprises adding sufficient nitrogen-free base to increase the pH to at least about
 10. 12. The method of claim 1, wherein said adding step comprises adding sufficient nitrogen-free base to increase the pH to at least about
 11. 13. The method of claim 1, wherein said adding step comprises adding sufficient nitrogen-free base to increase the pH to about 8 to about
 14. 14. The method of claim 1, wherein said adding step comprises adding sufficient nitrogen-free base to increase the pH to about 9 to about
 12. 15. The method of claim 1, wherein the aqueous composition is heated at a temperature of about 25° C. to about 200° C.
 16. The method of claim 1, wherein the aqueous composition is heated at a temperature of about 80° C. to about 150° C.
 17. The method of claim 1, wherein the aqueous composition is heated at a temperature of about 95° C. to about 130° C.
 18. The method of claim 1, wherein the aqueous composition is heated for about 30 minutes to about 3 hours.
 19. The method of claim 1, wherein the aqueous composition is heated for about 30 minutes to about 1.5 hours.
 20. The method of claim 1, wherein said heating step is conducted in atmospheric air and under atmospheric pressure.
 21. The method of claim 1, wherein the aqueous composition further comprises a reducing sugar or a precursor or derivative thereof.
 22. The method of claim 21, wherein the reducing sugar is selected from the group consisting of glucose, fructose, sucrose, mannose, galactose, rhamnose, and mixtures thereof.
 23. The method of claim 21, wherein the concentration of the reducing sugar is about 1 to about 20 percent by weight based on the weight of the aqueous composition.
 24. The method of claim 21, wherein the concentration of the reducing sugar is about 2 to about 10 percent by weight based on the weight of the aqueous composition.
 25. The method of claim 1, further comprising applying the aqueous composition to a smokable material.
 26. The method of claim 25, wherein the smokable material is tobacco.
 27. The method of claim 25, wherein the aqueous composition is applied as a top dressing or casing.
 28. The method of claim 1, further comprising applying the aqueous composition to insoluble tobacco pulp to form a reconstituted tobacco material.
 29. A method of producing flavorful and aromatic compounds from tobacco, comprising: providing an aqueous tobacco composition comprising water and a tobacco material, the tobacco material comprising solid pieces of whole tobacco or at least one aqueous tobacco extract; adding an amount of a nitrogen-free base to the aqueous composition sufficient to increase the pH of the aqueous composition to at least about 9; and heating the aqueous composition at a temperature of about 80° C. to about 150° C. for a time sufficient to produce flavorful and aromatic compounds.
 30. The method of claim 29, wherein the aqueous composition is heated at a temperature of about 95° C. to about 130° C.
 31. The method of claim 29, wherein the nitrogen-free base is selected from the group consisting of hydroxides of an alkali metal or an alkaline-earth metal, carbonates of an alkali metal or alkaline earth metal, and alkoxides of an alkali metal or alkaline earth metal.
 32. The method of claim 29, wherein the aqueous composition further comprises a reducing sugar or a precursor or derivative thereof.
 33. The method of claim 32, wherein the reducing sugar is selected from the group consisting of glucose, fructose, sucrose, mannose, galactose, rhamnose, and mixtures thereof.
 34. The method of claim 29, wherein said adding step comprises adding sufficient nitrogen-free base to increase the pH to at least about
 10. 35. The method of claim 29, wherein said adding step comprises adding sufficient nitrogen-free base to increase the pH to at least about
 11. 36. A method of producing flavorful and aromatic compounds from tobacco, comprising: providing an aqueous tobacco composition comprising water, at least one reducing sugar, and a tobacco material, the tobacco material comprising solid pieces of whole tobacco or at least one aqueous tobacco extract; adding an amount of a nitrogen-free base to the aqueous composition sufficient to increase the pH of the aqueous composition to at least about 9, the nitrogen-free base being a hydroxide of an alkali metal or an alkaline-earth metal; and heating the aqueous composition for a time and under conditions sufficient to produce flavorful and aromatic compounds.
 37. The method of claim 36, wherein the aqueous composition is heated at a temperature of about 80° C. to about 150° C.
 38. The method of claim 36, wherein the reducing sugar is selected from the group consisting of glucose, fructose, sucrose, mannose, galactose, rhamnose, and mixtures thereof.
 39. The method of claim 36, wherein the reducing sugar comprises high fructose corn syrup. 